The present invention relates to temperature sensors.
Generally, a temperature sensor is composed of analog circuitry where either an output voltage or current signal is generated that is proportional to ambient temperature. The analog circuitry's signal-to-temperature gain is typically very small (e.g., below a few mV). Therefore, induced offsets, either voltage or current, or component mismatch can result in substantial temperature sensor inaccuracies. Further, analog-to-digital conversion errors can add more inaccuracies to the temperature sensing process. For example, unstable reference voltages used in a analog-to-digital converter (ADC) can cause inaccurate variances such as gain errors in the temperature sensor results.
To mitigate these inaccuracies, conventional systems employ a post-trimming procedure on both the analog circuitry and the ADC reference voltage generator. The post-trimming procedure would test and tune each temperature sensor in a manufacturing lot individually. Thus, post-trimming significantly increases production costs by increasing testing time for multiple temperature testing and increasing additional wafer and die cost to implement post-trimming circuitry such as special electrical fuses. As a result, post-trimming restricts mass production capability and, consequently, temperature sensor integration.
Hence, the inventors recognized a need in the art for a low cost yet accurate temperature sensor.